[css3-regions][cssom] Bubbling for the regionLayoutUpdate event

Hello!

The Regions spec states that the regionLayoutUpdate event should be bubbling. When this event was dispatched on the region this was very easy to understand as they were DOM elements. Now, the NamedFlow object is the target, which is not clearly positioned in  the DOM hierarchy. How is the bubbling supposed to behave for this event? Should it be possible to listen for the event on the parent document and determine the NamedFlow from the event target?

Thanks!
Andrei.